Front-wheel suspension device for saddle riding vehicle

ABSTRACT

A motorcycle includes: a front swing arm; a fork holder coupled to the front swing arm in a swingable manner; a front fork steerably supported by the fork holder; and a front cushion unit. In a front-wheel suspension device, one end of the front cushion unit is coupled to the body frame, and the other end of the front cushion unit is coupled to the fork holder.

INCORPORATION BY REFERENCE

The present application claims priority under 35 U.S.C. § 119 toJapanese Patent Application No. 2018-184554 filed on Sep. 28, 2018. Thecontent of the application is incorporated herein by reference in itsentirety.

TECHNICAL FIELD

The present invention relates to front-wheel suspension devices forsaddle riding vehicles.

BACKGROUND ART

Conventionally, there are some known front-wheel suspension devices forsaddle riding vehicles in which a swing arm is composed of an upper armand a lower arm and the swing arm connects a body frame and a supportmember (fork holder) which rotatably supports a front fork, and acushion member (buffer) spans between the body from and the lower arm(see, e.g., Patent literature 1).

CITATION LIST Patent Literature

[Patent Literature 1] JP-A No. 2016-179796

SUMMARY OF INVENTION Technical Problem

According to Patent Literature 1, the coupling of a lower end of thebuffer to the lower arm places a constraint on the shape of the lowerarm, and this makes difficult to ensure a clearance between theunderside of the lower arm and a shoulder of the front fork which isrotated when the front wheel is steered through the handlebar, andtherefore the steering angle of the front wheel is limited. Further,even in the front-wheel suspension device in which the front-wheel sidearea is supported through the swing arm by the body frame, animprovement in the riding comfort of the vehicle is desired.

It is an object of the present invention to provide a front-wheelsuspension device of a saddle riding vehicle in which widening of asteering angle and an increase in riding comfort of the vehicle areachieved.

Solution to Problem

According to a first aspect of the present invention, a front-wheelsuspension device of a saddle riding vehicle includes: a swing arm (161)including an upper arm (165) and a lower arm (166) that are mounted to abody frame (11) in a swingable manner; a fork holder (162) that iscoupled to the upper arm (165) and the lower arm (166) in a swingablemanner; a front fork (53) that is steerably supported by the fork holder(162) and also that supports a front wheel (14); and a buffer (58) thathas one end coupled to the body frame (11). In the front-wheelsuspension device of the saddle riding vehicle, the buffer (58) has theother end coupled to the fork holder (162).

According to a second aspect of the present invention, the lower arm(166) may be coupled at a coupling site (122) to the body frame (11),and, as viewed in the side view of the vehicle, the coupling site (122)may be placed in front of a cylinder section (68) of an engine (41).

According to a third aspect of the present invention, further, the lowerarm (166) may be coupled at a coupling site (122) to the body frame(11), and, as viewed in the side view of the vehicle, the coupling site(122) may be placed forward of a handlebar grasping portion (45 d).

According to a fourth aspect of the present invention, further, the forkholder (162) and the buffer (58) may be coupled at a coupling site(168), and, as viewed in the side view of the vehicle, the coupling site(168) may be placed upward of a coupling site (122) of the lower arm(166) to the body frame (11).

According to a fifth aspect of the present invention, further, thecoupling site (168) between the fork holder (162) and the buffer (58)may be placed upward of the lower arm (166).

Advantageous Effects of Invention

According to the first aspect of the present invention, because theother end of the buffer is coupled to the fork holder, an increase inthe degree of freedom in the design of a shape of the lower arm can beenabled. This facilitates ensuring clearance between the lower arm and apart of the front fork which is rotated when the handlebar is steered,and therefore a wider steering angle can be enabled. Further, the loadthat acts from a road surface toward the fork holder is divided by theload that acts downward from the lower coupling site of the buffer tothe fork holder, and the load ratio (cushion ratio) obtained by thedividing can be increased. This enables an improvement in operability ofthe buffer, and in turn an improvement in the riding comfort of thevehicle.

According to the second aspect of the present invention, the couplingsite of the lower arm to the body frame is placed in front of thecylinder section of the engine as viewed in the side view of thevehicle. Because of this, the lower arm can be located near the cylindersection of the engine so that the front section of the vehicle body canbe made compact in size.

According to the third aspect of the present invention, further, thecoupling site of the lower arm to the body frame is placed forward ofthe handlebar grasping portion as viewed in the side view of thevehicle. Because of this, the front section of the vehicle body can bemade compact in size by placing the lower arm near the rider who holdsthe handlebar grasping portions.

According to the fourth aspect of the present invention, further, asviewed in the side view of the vehicle, the coupling site between thefork holder and the buffer is placed upward of the coupling site of thelower arm to the body frame. Because of this, when one end of the bufferis attached to or detached from the fork holder, the buffer can bereadily attached to or detached from the fork holder from above, andthus the working efficiency can be improved.

According to the fifth aspect of the present invention, further, becausethe coupling site between the fork holder and the buffer is placedupward of the lower arm, the buffer can be readily attached to ordetached from the fork holder, and thus the working efficiency can beimproved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a left side view illustrating a motorcycle including afront-wheel suspension device according to a first embodiment of thepresent invention.

FIG. 2 is a left side view illustrating a front body section of themotorcycle (the first embodiment).

FIG. 3 is a sectional view of the front body section (the firstembodiment).

FIG. 4 is a sectional view taken along IV-IV line of FIG. 2 (the firstembodiment).

FIG. 5 is a perspective view illustrating a front body section of amotorcycle including a front-wheel suspension device according to asecond embodiment.

FIG. 6 is a sectional view illustrating the front-wheel suspensiondevice (the second embodiment).

FIG. 7 is an action diagram illustrating the action of the front-wheelsuspension device (the second embodiment).

DESCRIPTION OF EMBODIMENTS

Embodiments according to the present invention will now be describedwith reference to the accompanying drawings. It is noted that,throughout the description, words for directions such as front, rear,left, right, upward and downward are used in conformity with directionswith respect to the vehicle body unless otherwise stated. Also, in eachdrawing, a reference sign FR denotes the front of the vehicle body, areference sign UP denotes the upper side of the vehicle body and areference sign LH denotes the left of the vehicle body.

First Embodiment

FIG. 1 is a left side view illustrating a motorcycle 10 including afront-wheel suspension device 20 according to a first embodiment of thepresent invention.

The motorcycle 10 includes: a front wheel 14 that is supported at afront portion of a body frame 11 through a front swing mechanism 12; arear wheel 17 that is supported at a rear portion of the body frame 11through a rear swing arm 16; and a seat 18 that is supported on an upperportion of the body frame 11. The motorcycle 10 is a saddle ridingvehicle on which a rider and a pillion passenger sit astride the seat18.

The body frame 11 includes a pair of left and right upper frames 21, atop frame 22, a pair of left and right pivot frames 23, a pair of leftand right seat frames 24, a pair of left and right sub-frames 26, a pairof left and right down frames 27, and a pair of left and right lowerframes 28.

The left and right upper frames 21 are placed above an engine 41, andthe upper frames 21 are bent in an upward protruding shape. A fuel tank43 is supported on upper portions of the upper frames 21. The top frame22 is composed of: a head pipe 31 that forms an upper end; and aplurality of head-pipe support frames 32 that are attached to the leftand right upper frames 21 to support the head pipe 31. The head pipe 31supports rotatably a handlebar steering shaft 46 on which a handlebar 45is mounted (see FIG. 3).

The left and right pivot frames 23 extend downward from rear ends of theupper frames 21, and the pivot frames 23 support a pivot shaft 48 thatextends in a vehicle width direction. The left and right seat frames 24extend rearward from upper ends of the left and right pivot frames 23,to support the seat 18.

Each of the left and right sub-frames 26 connects the correspondingpivot frame 23 and the corresponding seat frame 24. The left and rightdown frames 27 extend respectively downward and obliquely rearward fromlower front ends of the respective left and right upper frames 21. Theleft and right down frames 27 also support the engine 41 in cooperationwith the left and right pivot frames 23. The left and right lower frames28 extend respectively rearward from lower ends of the left and rightdown frames 27, so that the rear ends of the lower frames 28 areconnected to the lower ends of the respective left and right pivotframes 23.

The front swing mechanism 12 is configured to include: a front swing arm51 that is supported at the front portion of the body frame 11 in aswingable manner; a fork holder 52 that is coupled to the front swingarm 51 in a swingable manner; and a front fork 53 that is supported bythe fork holder 52 in a rotatable manner.

The front swing arm 51 is configured to include: a pair of left andright upper arms 55 that couple upper portions of the left and rightupper frames 21 and an upper portion of the fork holder 52; and a pairof left and right lower arms 56 that couple the lower ends of the leftand right upper frames 21 and a lower portion of the fork holder 52.

The fork holder 52 is a cylindrical shaped member, and tilts rearwardsuch that the upper end is located in a more rearward position of thevehicle than the lower end.

The front fork 53 has an upper portion inserted into the fork holder 52,and thus the front fork 53 is rotatably supported by the fork holder 52.The upper end of the front fork 53 is coupled to the handlebar 45through a link mechanism 61, and the front wheel 14 is supported at thelower end of the front fork 53 through an axle 63.

A front cushion unit 58 serving as a buffer is placed to span betweenthe left and right upper frames 21 and the left and right lower arms 56.

The aforementioned front swing mechanism 12 (the front swing arm 51, thefork holder 52, the front fork 53) and the front cushion unit 58 form afront-wheel suspension device 20 that suspends the front wheel 14.

A front end of the rear swing arm 16 is attached to the pivot shaft 48in a vertically swingable manner, and the rear wheel 17 is supported ata rear end of the rear swing arm 16 through an axle 65.

A pair of left and right rear cushion units 66 serving as buffers isplaced to span between the left and right rear ends of the rear swingarms 16 and the left and right of the rear portion of the body frame 11,respectively.

The engine 41 includes a crankcase 67 and a cylinder section 68 thatextends upward and obliquely forward from a front portion of thecrankcase 67, and the engine 41 includes a cylinder head 71 on thecylinder section 68. An intake device 72 is connected to a rear side ofthe cylinder head 71, and the intake device 72 includes an air cleanerand/or the like. An exhaust device 74 is connected to a front side ofthe cylinder head 71. The exhaust device 74 includes a plurality ofexhaust pipes 75 which are connected to the cylinder head 71, and theexhaust device 74 also includes a muffler 76 connected to the rear endof the plurality of exhaust pipes 75.

The handlebar 45 is mounted with a meter 81 and a pair of left and rightrearview mirrors 82.

An upper portion of the body frame 11 and a front portion of the fueltank 43 are covered from the lateral sides with a pair of left and rightfront covers 85.

The front wheel 14 is covered from above with a front fender 87, whilethe rear wheel 17 is covered from above with a rear fender 88.

FIG. 2 is a left side view illustrating a front body section of themotorcycle 10 (the first embodiment).

The body frame 11 includes a pair of left and right tubular loop-shapedframes 35 each of which is shaped endlessly to surround the engine 41.The top frame 22 is attached to upper portions of the left and rightloop-shaped frames 35.

The left and right loop-shaped frames 35 are configured to include thepair of left and right upper frames 21, the pair of left and right pivotframes 23, the pair of left and right down frames 27, and the pair ofleft and right lower frames 28. The left and right loop-shaped frames 35are connected by a plurality of cross pipes (not shown) which extend inthe vehicle width direction.

The engine 41 has a front portion supported by a pair of left and rightfront engine hangers 91 that are provided respectively on the left andright down frames 27. The engine 41 also has a rear portion supported bya pair of left and right upper rear engine hangers 92 and a pair of leftand right lower rear engine hangers 93, the left and right upper rearengine hangers 92 and the left and right lower rear engine hangers 93being correspondingly provided on the left and right pivot frames 23.

Each of the left and right upper arms 55 is formed in a linear shape. Afront end 55 a of the upper arm 55 is coupled to an upper portion of thefork holder 52, and a rear end 55 b of the upper arm 55 is coupled to anupper portion of the corresponding upper frame 21.

Each of the left and right lower arms 56 is formed in an upwardprotruding bent shape. A front end 56 a of the lower arm 56 is coupledto a lower portion of the fork holder 52, and a rear end 56 b of thelower arm 56 is coupled to a lower end of the corresponding upper frame21.

An upper end 58 b of the front cushion unit 58 is coupled to an upperconnecting shaft 95 in a swingable manner, and the upper connectingshaft 95 spans between the left and right upper frames 21. A lower end58 a of the front cushion unit 58 is coupled to a lower connecting shaft96 in a swingable manner, and the lower connecting shaft 96 spansbetween the left and right lower arms 56.

FIG. 3 is a sectional view of the front body section (the firstembodiment), and FIG. 3 shows a vertical section taken along a vehicleaxis extending in the front-rear direction while passing through thecenter in the vehicle width direction of the motorcycle 10.

The fork holder 52 includes a hollow portion 52 a that is graduallyincreased in internal diameter as the hollow portion 52 a extends fromthe upper end toward the lower end. A front-wheel steering shaft 101 isrotatably inserted into the hollow portion 52 a.

The front-wheel steering shaft 101 is a tubular member that is graduallyincreased in external diameter as the front-wheel steering shaft 101extends from the upper end toward the lower end. The front-wheelsteering shaft 101 is rotatably supported through a pair of bearings102, 103 by the fork holder 52.

The front fork 53 is configured to include the front-wheel steeringshaft 101 and a fork lower member 105 that is secured to the lower endof the front-wheel steering shaft 101.

The fork lower member 105 is integrally formed to include: a pair ofleft and right arm portions 105 a having lower ends at which the axle 63(see FIG. 1) is mounted; and a cross portion 105 b connecting upper endsof the respective left and right arm portions 105 a.

An axis line 101 a serves as a rotational axis of the front-wheelsteering shaft 101, and an inclination angle of the axis line 101 a froma vertical line 100 is a caster angle θ.

In the embodiment, because the upper arm 55 and the lower arm 56 havedifferent entire lengths, when the front wheel 14 is vertically movedrelative to the body frame 11, the caster angle θ varies. The depictedstate such as of the inclination angles of the upper arm 55 and thelower arm 56, the caster angle θ, and/or the like, illustrates the statewhere the body weight is applied to the front-wheel suspension device 20and also no occupant rides on (so-called “unloaded vehicle IGcondition”) (ditto for other figures).

The head pipe 31 includes a hollow portion 31 a, and the head pipe 31 isa tubular member that tilts rearward such that the upper end is locatedin a more rearward position of the vehicle than the lower end. Therearward-tilting handlebar steering shaft 46 is inserted into the hollowportion 31 a. The handlebar steering shaft 46 is rotatably supportedthrough a pair of bearings 107 by the head pipe 31. The handlebar 45 ismounted to the handlebar steering shaft 46.

The handlebar 45 has a handlebar base 45 a provided at the center in thevehicle width direction, and the handlebar 45 is provided in thehandlebar base 45 a with: a shaft through-hole 45 b that is fitted overthe handlebar steering shaft 46; and an L-shaped arm 45 c that is formedin a L-shape extending integrally in the forward direction and thedownward direction of the vehicle.

The L-shaped arm 45 c is placed in front of the head pipe 31. The linkmechanism 61 is coupled to the lower end of the L-shaped arm 45 c and tothe upper end of the front-wheel steering shaft 101.

The link mechanism 61 is configured to include an upper link 111 and alower link 112. The upper link 111 has one end coupled to the L-shapedarm 45 c in a swingable manner, and the lower link 112 is coupled toboth the other end of the upper link 111 and the upper end of thefront-wheel steering shaft 101 in a swingable manner.

Specifically, a link support member 113 is attached to the upper end ofthe front-wheel steering shaft 101, and the lower link 112 is coupled toa front end of the link support member 113 in a swingable manner.

The upper end of the upper link 111 is coupled through a connectingshaft 115 to the L-shaped arm 45 c in a swingable manner. The lower endof the upper link 111 and the upper end of the lower link 112 arecoupled together through a connecting shaft 116 in a swingable manner.The lower end of the lower link 112 is coupled through a connectingshaft 117 to the link support member 113 in a swingable manner.

The upper frame 21 includes a tilt portion 21 b that extends forward andobliquely downward from an uppermost portion 21 a while bending, theuppermost portion 21 a being placed in an uppermost position of theupper frame 21. The tilt portion 21 b is configured to include an uppertilt portion 21 c and a lower tilt portion 21 d. The upper tilt portion21 c extends forward and obliquely downward from the uppermost portion21 a, and the lower tilt portion 21 d extends forward and obliquelydownward at a steeper angle than the upper tilt portion 21 c from alower end of the upper tilt portion 21 c. A connection point between theupper tilt portion 21 c and the lower tilt portion 21 d is a bendingbend portion 21 e.

The lower arm 56 includes a bend portion 56 e between the upper frame 21and the fork holder 52 in the vehicle longitudinal direction, the bendportion 56 e bending in an upward protruding shape.

The upper end 58 b of the front cushion unit 58 is coupled through theupper connecting shaft 95 to the uppermost portion 21 a of the upperframe 21. The lower end 58 a of the front cushion unit 58 is alsocoupled through the lower connecting shaft 96 to the bend portion 56 eof the lower arm 56.

The front cushion unit 58 extends along the tilt portion 21 b(specifically, the upper tilt portion 21 c) of the upper frame 21, andalso the front cushion unit 58 overlaps the tilt portion 21 b(specifically, the upper tilt portion 21 c and an upper portion of thelower tilt portion 21 d) as viewed in the side view of the vehicle.

The rear end 55 b of the upper arm 55 is coupled through a connectingshaft 121 to the bend portion 21 e of the upper frame 21 in a swingablemanner. Also, the rear end 56 b of the lower arm 56 is coupled through aconnecting shaft 122 to the lower end of the lower tilt portion 21 d ina swingable manner. The connecting shaft 121 overlaps the front cushionunit 58 as viewed in the side view of the vehicle.

The front end 55 a of the upper arm 55 is coupled through a connectingshaft 123 to an upper portion of the fork holder 52 in a swingablemanner. The connecting shaft 123 overlaps the front-wheel steering shaft101 as viewed in the side view of the vehicle.

The front end 56 a of the lower arm 56 is coupled through a connectingshaft 124 to a frontward protrusion 52 b in a swingable manner, and thefrontward protrusion 52 b is integrally formed on a lower portion of thefork holder 52.

Each of the upper arms 55 and the lower arms 56 is positioned upwardtoward the front. The connecting shaft 123 is located upward of theconnecting shaft 121, and the connecting shaft 124 is located upward ofthe connecting shaft 122.

The lower connecting shaft 96 is located upward of a straight line 130that passes through axes 122 a, 124 a (points indicated with filledcircles) of the respective connecting shafts 122, 124 on the lower arm56. The lower connecting shaft 96 is also located upward of theconnecting shaft 122.

The handlebar 45 includes grips 45 d placed at both the left and rightends of the handlebar 45 in order for the rider to hold the grips 45 d.As viewed in the side view of the vehicle, the connecting shaft 122 onthe rear end 56 b of the lower arm 56 is located forward of a verticalline 110 that extends vertically through the front end of thecorresponding grip 45 d.

FIG. 4 is a sectional view taken along IV-IV line of FIG. 2 (the firstembodiment), FIG. 4 being a cutaway view along a plane passing throughthe left and right connecting shafts 121, 123.

The fork holder 52 integrally includes a pair of left and right sidewardextended portions 52 c that extend from the center in the vehicle widthdirection toward the outside in the vehicle width direction. Internalthreads 52 d are formed respectively in the left and right sidewardextended portions 52 c.

The connecting shafts 123, which are formed of stud bolts, are screwedrespectively into the internal threads 52 d of the respective left andright sideward extended portions 52 c, and the front ends 55 a of theupper arms 55 are coupled respectively through bearings 134 to the leftand right connecting shafts 123 in a swingable manner. The front-wheelsteering shaft 101 is placed between the left and right connectingshafts 123.

As illustrated in FIG. 3 and FIG. 4, the left and right sidewardextended portions 52 c overlap the front-wheel steering shaft 101 asviewed in the side view of the vehicle. Further, the connecting shafts123 also overlap the front-wheel steering shaft 101 as viewed in theside view of the vehicle.

Conventionally, a connecting shaft for coupling each of the left andright upper arms to a fork holder is located forward of a front-wheelsteering shaft. However, in the embodiment, the left and rightconnecting shafts 123 are placed on both sides in the vehicle widthdirection of the front-wheel steering shaft 101, and thereby the leftand right connecting shafts 123 are placed in more rearward positions ofthe vehicle than the convention.

This enables a reduction in entire length of each of the left and rightupper arms 55 to increase the rigidity of the upper arms 55 (inparticular, the torsional rigidity when the left and right upper arms 55are twisted, and the laterally flexural rigidity), and therefore higherrigidity of the front-wheel suspension device 20 can be achieved.Further, by shortening the entire length of each of the left and rightupper arms 55, the front-wheel suspension device 20 may be made smallerin size, compact.

The left and right upper arms 55 and the left and right lower arms 56are arranged such that the distance between the upper arms 55 and thedistance between the lower arms 56 taper down gradually toward the frontof the vehicle. Also, the pair of left and right upper arms 55 and thepair of left and right lower arms 56 are arranged at a vertical distancefrom each other (see also FIG. 3), and also vertically overlap eachother. The left and right upper arms 55 are arranged along the left andright lower arms 56.

In order to prevent the front ends 55 a of the respective left and rightupper arms 55 from coming out of the connecting shafts 123, each frontend 55 a is retained by a nut 135 and a locknut 136 which are screwedonto the end of the connecting shaft 123.

A hollow portion 21 f and a bolt through hole 21 g are formed in thetilt portion 21 b (specifically, the bend portion 21 e) of each of theleft and right upper frames 21, and the bolt through hole 21 g extendsoutward in the vehicle width direction from the bottom of the hollowportion 21 f to pass through the tilt portion 21 b in the vehicle widthdirection.

The rear end 55 b of each of the left and right upper arms 55 isattached to the tilt portion 21 b in a swingable manner by thebolt-shaped connecting shaft 121, a nut 143 and a locknut 144, thebolt-shaped connecting shaft 121 being passed through the bolt throughhole 21 g of the tilt portion 21 b, the nut 143 and the locknut 144being screwed onto the end of the connecting shaft 121.

The front ends 56 a of the respective left and right lower arms 56 arearranged on both sides of the frontward protrusion 52 b of the forkholder 52, and the front ends 56 a are coupled together by thebolt-shaped connecting shaft 124 that passes through the front end 56 a,the frontward protrusion 52 b and the front end 56 a. A nut 146 isscrewed onto the end of the connecting shaft 124.

The rear ends 56 b of the lower arms 56 are coupled through thebolt-shaped connecting shaft 122 to boss portions 21 h that are formedrespectively on sides of lower ends in the tilt portions 21 b of therespective left and right upper frames 21. The left and right bossportions 21 h are placed on an extension line of a front cross pipe 148that extends in the vehicle width direction to span between the left andright upper frames 21.

The cylinder head 71 is placed at the rear of the front cross pipe 148.

Second Embodiment

FIG. 5 is a perspective view illustrating a front body section of amotorcycle 10A including a front-wheel suspension device 160 accordingto a second embodiment. In the second embodiment, like reference signsare used to refer to like components in the first embodiment, anddetails are omitted.

The front-wheel suspension device 160 differs in a front swing mechanism12A from the front-wheel suspension device 20 in the first embodiment.

The front swing mechanism 12A is configured to include a front swing arm161, a fork holder 162, and the front fork 53. Also, the front swingmechanism 12A and the front cushion unit 58 form the front-wheelsuspension device 160.

The front swing arm 161 is composed of the upper arm 55 and a lower arm166, the upper arm 165 and the lower arm 166 being supported in a frontportion of the body frame 11 in a swingable manner.

The upper arm 165 is identical with the upper arm 55 (see FIG. 1) in thefirst embodiment, but the different reference signs are used fordistinction.

The lower arm 166 is integrally formed to include: a lateral extendedportion 166 a that extends in the vehicle width direction; and a pair ofleft and right frontward extended portions 166 b that extend forwardfrom both ends of the lateral extended portion 166 a.

Front ends 166 c of the respective left and right frontward extendedportions 166 b are coupled through the connecting shaft 124 to a lowerportion of the fork holder 162. Ends 166 d on both sides of the lateralextended portion 166 a are coupled respectively through the connectingshafts 122 to the lower ends of the tilt portions 21 b of the left andright upper frames 21.

The connecting shafts 122 are located in front of the cylinder section68 (specifically, the cylinder head 71) of the engine 41 as viewed inthe side view of the vehicle.

The fork holder 162 is provided with a coupling site (not shown) locatedin a rear portion, and the front cushion unit 58 is coupled to thecoupling site.

FIG. 6 is a sectional view illustrating the front-wheel suspensiondevice 160 (the second embodiment), and FIG. 6 shows a vertical sectiontaken along a vehicle axis extending in the front-rear direction whilepassing through the center in the vehicle width direction of themotorcycle 10A.

The fork holder 162 differs only in a rearward protrusion 162 a from thefork holder 52 (see FIG. 3) in the first embodiment.

The rearward protrusion 162 a is a portion protruding rearward from arear portion of a middle portion in the longitudinal direction of thefork holder 162. The lower end 58 a of the front cushion unit 58 iscoupled through the lower connecting shaft 168 to the rearwardprotrusion 162 a in a swingable manner.

The lower connecting shaft 168 is located upward of the connecting shaft122, and the lower connecting shaft 168 is also located upward of thestraight line 130. Further, the lower connecting shaft 168 is locatedupward of the lower arm 166.

In an upper portion of the fork holder 162, the fork holder 162integrally includes a pair of left and right sideward extended portions52 c that extend outward in the vehicle width direction from a centralportion in the vehicle width direction, as in the case of the forkholder 52, in FIG. 4. The internal threads 52 d are formed respectivelyin the left and right sideward extended portions 52 c. The connectingshafts 123 are screwed into the left and right internal threads 52 d,and the front ends 55 a of the upper arm 165 are coupled through thebearings 134 to the left and right connecting shafts 123 in a swingablemanner, respectively.

As described above, by coupling the front cushion unit 58 to the forkholder 162, the fork holder 162 with high strength and high rigidity canbe used to support the front cushion unit 58, and thus the strength andrigidity of the front-wheel suspension device 160 can be increased.Further, the lower end 58 a of the front cushion unit 58 is placed in afurther frontward position of the vehicle, so that the entire length ofthe front cushion unit 58 can be longer to increase the stroke of thefront cushion unit 58. As a result, the riding comfort of the motorcycle10A can be improved.

The lower arm 166 differs from the lower arm 56 (see FIG. 4) in thefirst embodiment in that no lower connecting shaft 96 (see FIG. 3) isprovided for coupling the front cushion unit 58. In this manner, becausea shaft through hole for insertion of the lower connecting shaft 96 isnot formed in the lower arm 166, the strength and rigidity of the lowerarm 166 can be increased.

The front end 166 c of the lower arm 166 is coupled to the frontwardprotrusion 52 b of the fork holder 162 through the connecting shaft 124,and each end 166 d of the lower arm 166 is coupled to the lower end ofthe tilt portion 21 b of the upper frame 21 through the connecting shaft122.

The connecting shaft 122 is located forward of the vertical line 110passing through the front end of the grip 45 d, as viewed in the sideview of the vehicle.

FIG. 7 is an action diagram illustrating the action of the front-wheelsuspension device 160 (the second embodiment).

It is noted that the upper frame 21, the fork holder 162 and the lowerarm 166 are indicated by a dash-dot-dot line, and the front cushion unit58 is schematically shown by a solid line or a broken line. The solidline shows the front cushion unit 58 of an example (the embodiment)where the lower end of the front cushion unit 58 is coupled to the forkholder 162. The broken line shows the front cushion unit 58 of acomparative example where the lower end of the front cushion unit 58 iscoupled to the lower arm 166.

Assuming that: L1 is the distance between the connecting shaft 122 andthe connecting shaft 124 of the lower arm 166; L2 is the distancebetween the connecting shaft 170 and the connecting shaft 122 if thelower end of the front cushion unit 58 is coupled to the lower arm 166;and L3 is the distance between the connecting shaft 122 and the lowerconnecting shaft 168. Note that the distances L1, L2, L3 are distancesin the front-rear direction.

If the lower end of the front cushion unit 58 is coupled to the forkholder 162 as in the example, in compared with the case where the frontcushion unit 58 is coupled to the lower arm 166 as in the comparativeexample, no interference occurs between the connecting shaft and thefork holder 162. Because of this, L3>L2 can be held.

The following is a description of action occurring, for example, whenthe fork holder 162, together with the axle 63 of the front wheel, is tobe moved upward relative to the upper frames 21.

Assume, in the comparative example and the example, that the load actingupward from the axle 63 is F, and the load acting upward on theconnecting shaft 124 of the lower arm 166 is F1, and assume, in thecomparative example, that the load acting downward from the connectingshaft 170 is F2. Then, a load balance is expressed by the following:

F=F1  (1)

F1·L1=F2·L2  (2)

Also, assume, in the example, that the load acting downward from thelower connecting shaft 168 is F3. Then, a load balance with respect tothe upper connecting shaft 95 as a base point is expressed by thefollowing:

F1=F3  (3)

From the above equations (2) and (3), in the comparative example,F2=F1*(L1/L2) can be given, and in the example, F3=F1 can be given. Inturn, from these equations, F2=F3*(L1/L2) results. Because of L1>L2,F2>F3 results. Also, for a cushion ratio, (F/F2)<(F/F3) results.

In this manner, the cushion load F3 of the front cushion unit 58 in theexample is smaller than the cushion load F2 of the front cushion unit 58in the comparative example. Also, the cushion ratio (F/F3) in theexample is larger than the cushion ratio (F/F2) in the comparativeexample.

From the above, in the example, the absorption of impact energy isfacilitated and thus the ride comfort can be improved as compared withthe comparative example.

As illustrated above in FIG. 5 and FIG. 6, the motorcycle 10 as a saddleriding vehicle includes the front swing arm 161 as a swing arm, the forkholder 162, the front fork 53, and the front cushion unit 58 as abuffer.

The front swing arm 161 is composed of the upper arms 165 and the lowerarms 166, the upper arms 165 and the lower arms 166 being mounted to thebody frame 11 in a swingable manner. The fork holder 162 is coupled tothe upper arms 165 and the lower arms 166 in a swingable manner. Thefront fork 53 is steerably supported by the fork holder 162, and alsothe front fork 53 supports the front wheel 14. The front cushion unit 58has one end coupled to the body frame 11. In the front-wheel suspensiondevice 160, the other end of the front cushion unit 58 is coupled to thefork holder 162.

With the configuration, because the front cushion unit 58 is coupleddirectly to the fork holder 162, an increase in the degree of freedom inthe design of a shape of the lower arm 166 can be enabled. This resultsin the facilitation of the ensuring of clearance between the lower arms166 and a part of the front fork 53 which is rotated when the handlebar45 is steered, and thus the steering angle of the front wheel 14 can bewidened. Further, the load F that acts from a road surface toward thefork holder 162 is divided by the load F3 that acts downward from thelower coupling site 168 which is a coupling site of the front cushionunit 58 to the fork holder 162, and the load ratio (cushion ratio) F/F3thus obtained by the diving can be increased with respect to a loadratio (cushion ratio) F/F2 in the comparative example. This enables anincrease in the cushion ratio of the front-wheel suspension device 160to improve the operability of the front cushion unit 58, and in turn theriding comfort of the motorcycle 10A can be improved.

As illustrated in FIG. 6, also, the connecting shaft 122 as a couplingsite of the lower arm 166 to the body frame 11 is placed in front of thecylinder section 68 (specifically, the cylinder head 71) of the engine41 as viewed in the side view of the vehicle.

With the configuration, the lower arm 166 is located near the cylindersection 68 of the engine 41 so that the front section of the vehiclebody can be made compact in size.

Also, as viewed in the side view of the vehicle, the connecting shaft122, which is a coupling site of the lower arm 166 to the body frame 11,is placed forward of the grip 45 d as a handlebar grasping portion.

With the configuration, the front section of the vehicle body can bemade compact in size by placing the lower arm 166 near the rider whoholding the grips 45 d.

Also, as viewed in the side view of the vehicle, the lower connectingshaft 168 as a coupling site between the fork holder 162 and the frontcushion unit 58 is placed upward of the connecting shaft 122 as acoupling site of the lower arm 166 to the body frame 11.

With the configuration, when one end of the front cushion unit 58 isattached to or detached from the fork holder 162, theattachment/detachment of the front cushion unit 58 to/from the forkholder 162 can be readily performed from above the lower arm 166, andthus the working efficiency can be improved.

Also, the lower connecting shaft 168 as a coupling site between the forkholder 162 and the front cushion unit 58 is placed upward of the lowerarm 166.

With the configuration, the attachment/detachment of the front cushionunit 58 to/from the fork holder 162 can be readily performed from abovethe lower arm 166, and thus the working efficiency can be improved.

The embodiments have been described to provide a merely illustrativeembodiment of the present invention, and thus any modification and anyapplication of the present invention can be possible without departingfrom the spirit and scope of the present invention.

For example, in the above embodiments, as illustrated in FIG. 4 and FIG.6, the pair of left and right sideward extended portions 52 c are placedin the upper portion of the fork holder 52, 162, and the left and rightsideward extended portions 52 c extend in the vehicle width direction,and the front ends of the left and right upper arms 55 (or the left andright upper arm 165) are coupled to the left and right sideward extendedportions 52 c through the connecting shafts 123, respectively. Likewise,a pair of left and right sideward extended portions extending in thevehicle width direction may be provided in a lower portion of the forkholder 52, 162, and the front ends of the left and right lower arms 56,166 may be coupled to the sideward extended portions through theconnecting shafts 124, respectively. In this case, the sideward extendedportions and the connecting shafts 124 may be placed to overlap thefront-wheel steering shaft 101 as viewed in the side view of thevehicle.

REFERENCE SIGNS LIST

-   -   10A . . . Motorcycle (saddle riding vehicle)    -   11 . . . Body frame    -   14 . . . Front wheel    -   41 . . . Engine    -   45 . . . Handlebar    -   45 d . . . Grip (handlebar grasping portion)    -   53 . . . Front fork    -   58 . . . Front cushion unit (buffer)    -   61 . . . Link mechanism    -   71 . . . Cylinder head    -   122 . . . Connecting shaft (coupling site)    -   160 . . . Front-wheel suspension device    -   161 . . . Front swing arm (swing arm)    -   162 . . . Fork holder    -   165 . . . Upper arm    -   166 . . . Lower arm    -   168 . . . Lower connecting shaft (coupling site)

1. A front-wheel suspension device of a saddle riding vehicle,comprising: a swing arm including an upper arm and a lower arm that aremounted to a body frame in a swingable manner; a fork holder that iscoupled to the upper arm and the lower arm in a swingable manner; afront fork that is steerably supported by the fork holder and also thatsupports a front wheel; and a buffer that has one end coupled to thebody frame, wherein the buffer has the other end coupled to the forkholder.
 2. The front-wheel suspension device of the saddle ridingvehicle according to claim 1, wherein the lower arm is coupled at acoupling site to the body frame, and, as viewed in the side view of thevehicle, the coupling site is placed in front of a cylinder section ofan engine.
 3. The front-wheel suspension device of the saddle ridingvehicle according to claim 1, wherein the lower arm is coupled at acoupling site to the body frame, and, as viewed in the side view of thevehicle, the coupling site is placed forward of a handlebar graspingportion.
 4. The front-wheel suspension device of the saddle ridingvehicle according to claim 1, wherein the fork holder and the buffer arecoupled at a coupling site, and, as viewed in the side view of thevehicle, the coupling site is placed upward of a coupling site of thelower arm to the body frame.
 5. The front-wheel suspension device of thesaddle riding vehicle according to claim 4, wherein the coupling sitebetween the fork holder and the buffer is placed upward of the lowerarm.